The subject matter disclosed herein relates to a transport control server (TCS), and in particular relates to the transport control server for calculating a communication path.
In recent years, for the purpose of achieving higher reliability and higher quality, a transport control server has been developed for controlling a plurality of network protocols and networks which connect communication paths between communication user points in an end-to-end relationship. Examples of the network protocol include MPLS (Multi-Protocol Label Switching), MPLS-TP (MPLS Transport Profile), PBB-TE (Provider Backbone Bridge Traffic Engineering), OpenFlow, GMPLS (General MPLS), and the like.
These protocols are used, for example, in a wide area network connecting user points and/or data centers, within a data center, and in a virtual network under-study by New Generation. Example of the wide area network include a company private line, L2VPN (Layer2 Virtual Private Line), L3 VPN (Layer3 VPN), and the like. The virtual network is a network, under study by GENI and the like, in which a transmitting device has functions, such as programmability, in order to logically divide a physical network resource and have flexibility.
In the transport control server, path calculation corresponding to scalability and flexibility is the subject. Scalability is the capability to respond to an increase of the number of transmitting devices, an increase of the number of communication paths, and the like. These increases and the like are caused by an increase of communication users, an increase of traffic per capita, network integration, and the like. Flexibility is the capability to reflect various operation policies, such as a request bandwidth, delay restrictions, the presence or absence of a standby path, a method for securing the bandwidth of a standby path, and the bandwidth use efficiency.
In a network divided and managed as a plurality of domains, a plurality of communication paths in each domain are managed as one link (herein, referred to as an abstract link). Then, when a path via a plurality of the domains is set in an end-to-end relationship, the path is calculated based on the information on an abstract link. Herein, this is referred to as hierarchical routing. A logical communication path connecting user points, nodes, and/or the like is referred to as a path.
Hereinafter, a conventional art related to the above-described problem is described.
In US Patent Application Publication No. 2010/051215, in selecting the shortest path by hierarchical distributed routing, the shortest path cost between border routers of a relevant lower subnetwork is acquired by a PCS (Path Computation Server) of a higher layer from a shortest-path list within an area which a PCS of a lower layer manages, and this cost is regarded as a virtual link cost, and based on the acquired virtual link cost between boundary nodes and the link cost between the subnetworks which the PCS of a higher layer manages, the shortest path from the point of origin to the end point is calculated. This enables to select the shortest path between calculation domains of a lower hierarchical layer.
In JP-A-2008-42670, a path calculation domain is determined, and then from a path calculation domain side in which an end-point node is present toward a path calculation domain in which an initial node is present, redundant paths within a domain are sequentially calculated by a path calculation unit in each path solution system. Then, the redundant paths within a domain which each path solution system calculated are connected together to calculate a redundant path between an initial node and an end-point node. This enables to efficiently calculate redundant paths (a working path and a standby path) in a multidomain network.
In JP-A-2007-19852, a path calculation program of each server of a plurality of customer networks selects root candidates within a distributed network, respectively, and then an optimum route is determined in cooperation with the path calculation program by hierarchically combining the root candidates. Thus, a technique can be provided, which, when a VPN service for coupling user networks (i.e., “customer networks”) using MPLS is provided, determines a path satisfying user's quality requirements in an end-to-end relationship, including also paths within a customer network, and which also achieves a differentiation in a customer network in accordance with SLA and further determines a backup path for failures.
In US Patent Application Publication No. 2008/0002664, a path calculation element is hierarchized, and thereby in the higher layer and lower layer of the path calculation element, the calculation domain of the path calculation element is mapped and a calculation task is hierarchically divided and the route calculation is performed in a parallel mode, so that the calculation amount which each path calculation element carries out can be reduced.